The conventional art has provided a share mode type injection head wherein voltage is applied to the electrode formed on a drive wall which is separating the channel so that shear deformation, is caused at the drive wall and the ink inside the channel is emitted from the nozzle using the pressure generated inside the channel at this time. As this share mode type injection head, an injection head provided with the so-called harmonica type head chip is known, wherein the drive walls made up of piezoelectric elements and the channels are arranged alternately, and a channel aperture is arranged on each of the front side and rear side (Patent Document 1, 2).
In the case of an injection head having such a harmonica type head chip, ink is supplied into each channel from the rear side of the head chip. Accordingly, an ink manifold is connected to the rear side of the head chip, and the ink stored in this ink manifold is supplied to each channel.
Incidentally, as disclosed in the Patent Documents 1 and 2, the rear side of such a head chip is provided with a flow path regulating member for regulating the flow of ink into the channel by reducing the area of the aperture on the channel inlet side.
FIG. 15 is a rear side view of the head chip 600 connected with a flow path regulating member 500. This drawing illustrates a harmonica type head chip 600 wherein the air channels 601 that do not emit ink and the ink channels 602 that emit ink are arranged alternately.
The flow path regulating member 500 utilizes a plastic film such as a sheet of polyimide having the size capable of covering almost all the surfaces on the rear side of the head chip 600. This film is bonded using an adhesive as an epoxy adhesive. Here the rear side of each air channel 601 provided on the head chip 600 is completely blocked and an ink inlet 501 is formed so as to conform to each ink channel 602, thereby reducing the area of the aperture on the rear side (on the side supplied with ink) of each ink channel 602. The ink inlet 501 is provided, for example, by laser processing in such a way as to have a diameter smaller than that of the aperture on the rear side of the ink channel 602.
As described above, the area of the aperture on the rear side of the ink channel is reduced by the flow path regulating member 500, whereby easy control of the ink meniscus in the nozzle is ensured and high-speed drive is enabled. Thus, this arrangement provides the advantage of enhancing the drive characteristics.
When all the channels arranged on the head chip are ink channels, the ink inlets of the flow path regulating member are arranged so as to correspond to all the channels.
[Patent Document 1] Unexamined Japanese Patent Application Publication No. 2004-90374
[Patent Document 2] Unexamined Japanese Patent Application Publication No. 2006-35454
When the aforementioned flow path regulating member is connected to the rear side of the head chip, the coated adhesive may ooze from the ink inlet. This requires a large quantity of adhesive to be coated. This involves such problems as the excess adhesive flowing into the channel to block the channel and to cause emission failure, or ink flowing into the air channel due to insufficient coating of the adhesive. Further, it becomes difficult to provide contact pressure from the flow path regulating member side due to the adhesive oozing out of the ink inlet when the flow path regulating member is connected. This requires a great care to be taken at the time of coating the adhesive and during the connection work, and has caused manufacturing difficulties in the conventional art.
To ensure that the adhesive from the ink inlet does not ooze out, it may be possible to make such arrangements that the ink inlet is formed by laser processing after the flow path regulating member has been connected to the rear side of the head chip. However, this requires complication positioning work, for example, by use of a microscope, for the purpose of ensuring that each ink inlet will conform to the position of each ink channel, with the result that workability is deteriorated. Moreover, there is no solution to the problem of the channel being clogged by the excess adhesive.
Further, when the area of the aperture on the rear side of the channel is to be reduced by the flow path regulating member, the ink inlet having a smaller area than that of the aperture on the rear side of the channel is formed approximately at the center of the aperture in the conventional flow path regulating member. Thus, the bubble having occurred inside the channel at the time of driving cannot easily get out of the ink inlet, and remains inside the channel. The bubble remaining inside the channel prevents a sufficient amount of the emission pressure from being applied to the ink, with the result that emission failure occurs.